1. Field of the Invention
The present invention generally relates to a method, system and software product used in computer-aided engineering analysis of a structure, more particularly to modeling spot welds in a finite element analysis.
2. Description of the Related Art
Finite element analysis (FEA) is a computerized method widely used in industry to model and solve engineering problems relating to complex systems such as three-dimensional non-linear structural design and analysis. FEA derives its name from the manner in which the geometry of the object under consideration is specified. With the advent of the modern digital computer, FEA has been implemented as FEA software. Basically, the FEA software is provided with a model of the geometric description and the associated material properties at each point within the model. In this model, the geometry of the system under analysis is represented by solids, shells and beams of various sizes, which are called elements. The vertices of the elements are referred to as nodes. The model is comprised of a finite number of elements, which are assigned a material name to associate with material properties. The model thus represents the physical space occupied by the object under analysis along with its immediate surroundings. The FEA software then refers to a table in which the properties (e.g., stress-strain constitutive equation, Young's modulus, Poisson's ratio, thermo-conductivity) of each material type are tabulated. Additionally, the conditions at the boundary of the object (i.e., loadings, physical constraints, etc.) are specified. In this fashion a model of the object and its environment is created.
FEA is becoming increasingly popular with automobile manufacturers for optimizing both the aerodynamic performance and structural integrity of vehicles. Similarly, aircraft manufacturers rely upon FEA to predict airplane performance long before the first prototype is built. Rational design of semiconductor electronic devices is possible with Finite Element Analysis of the electrodynamics, diffusion, and thermodynamics involved in this situation. FEA is utilized to characterize ocean currents and distribution of contaminants. FEA is being applied increasingly to analysis of the production and performance of such consumer goods as ovens, blenders, lighting facilities and many plastic products. In fact, FEA has been employed in as many diverse fields as can be brought to mind, including plastics mold design, modeling of nuclear reactors, analysis of the spot welding process, microwave antenna design, simulating of car crash and biomedical applications such as the design of prosthetic limbs. In short, FEA is utilized to expedite design, maximize productivity and efficiency, and optimize product performance in virtually every stratum of light and heavy industry. This often occurs long before the first prototype is ever developed.
One of the most challenging FEA tasks is to simulate an impact event such as car crash or metal forming. In a typical car, there are about 4,000-8,000 spot welds connecting 300-600 body parts to form the vehicle structure. For accurate simulation of the vehicle as a whole, those spot welds have to be modeled accurately. Spot welds are typically placed 2-3 centimeters apart, and each spot weld has a diameter between 4 to 9 millimeters. Traditionally, each of the spot welds has been modeled with a very short beam element (e.g., length of 1-2 millimeters) in FEA. As the modern computer improves, the finite element models representing a vehicle have become huge (e.g., more than 1,000,000 elements). Thereby, the size of each element becomes much smaller. Representing spot welds using beam elements are not adequate any more, instead solid elements are used. In certain cases, spot welds have been modeled with more than one solid element. As a result, it is very tedious and time consuming to create a cluster of solid elements to represent a single spot weld, when there are thousands of spot welds in one vehicle.
It is therefore desirable to have new improved method and system for generating solid elements to represent spot welds using the traditional spot weld input definition in a finite element analysis.